Heretofore known are various glutathione derivatives. Among them, S-(.alpha.,.beta.-dicarboxyethyl)glutathione is a substance found in the body which D. H. Calam and S. G. Waley (Biochem. J. 86, 226, 1963) discovered in the bovine crystalline lens but its physiological activity remained to be known for certain. However, the inventors of the present invention found that this compound has platelet aggregation inhibitory, antiinflammatory, antiallergic, antitumor and hepatic disorders inhibitory activities (Japanese Kokai Tokkyo Koho No. 63-8337 (1988), and Japanese Patent Application No. 1-79956 (1989), No. 1-183484 (1989), No. 1-251534 (1989) and No. 1-256370 (1989).
In search of glutathione derivatives which would be more efficiently absorbed by tissues, the inventors of the present invention synthesized new glutathione derivatives using glutathione (or monoesters thereof) and maleic acid or itaconic acid or an ester, amide or imide thereof respectively, and discovered that these compounds have excellent pharmacological activities. This discovery and subsequent research resulted in the present invention.